• Warming sign in the Arctic: Starving female polar bear challenges male for food

    A recent voyage by the National Geographic Explorer ship to the Arctic captured a female polar bear fighting a male for food. NBCNews.com's Dara Brown reports on the trip, which allowed experts to evaluate the environmental changes in the Arctic.

    By Miguel Llanos, NBC News

    Wildlife biologist Ian Bullock is a seasoned visitor to the Arctic, but even he was surprised by what he saw last month: a thin female polar bear, shadowed by her cub, trying to challenge a much bigger, stronger male for food.


    It wasn't much of a challenge, but it showed just how desperate she was, Bullock told NBC News on returning from his 10th straight summer cruise to the Arctic.

    That desperation, he feels, stems from the fact that the Arctic's summer sea ice — which polar bears using as floating stations from which to hunt seals — has been shrinking over the last few decades due to a warming Arctic, forcing polar bears into smaller areas and more intense competition. 

    "She was the thinnest female with cub I have ever seen," he said. "She had a single cub which implies she has already lost one other cub this year.

    "If she cannot feed, she cannot suckle her cub; with a hungry cub it is even harder for her to hunt effectively, so from what I saw her last cub is at risk and ultimately so is she," he added. "This is why she was challenging a big male with food. She was hungry enough to take a big risk." 

    In a video filmed during the National Geographic Explorer cruise to the Arctic's Svalbard region, Bullock said it looks like that reduced ice is "really putting the bears under stress."

    "The worst thing is when we've encountered bears, we've found them really packed in tight, in the last little areas of fast ice attached to land, or the last little patches of pack ice at sea," said Bullock, who served as a guide on the cruise ship. "And there they've been in competition."

    Polar bears are listed as "vulnerable" and in decline by the International Union for Conservation of Nature, which estimates the population at no more than 25,000 across the Arctic.

    The U.S., which has two Arctic regions where polar bears live, in 2008 listed its population as "threatened".

    Last year, researchers cited three incidents where polar bears might even have resorted to cannibalism due to warming and reduced sea ice.

    The diminished sea ice also got the attention of the National Geographic Explorer's skipper.

    Captain Leif Skog told NBC News that he had e-mailed his boss, Sven Lindblad of Lindblad Expeditions, to describe "a shocking escalation of the reduction of sea ice."

    One data graph he monitored daily, showing the total volume of Arctic sea ice, "could be called the death spiral of the Arctic sea ice," he said in his e-mail to Lindblad.

    Because of the reduced sea ice, he added, the cruise was able to visit northeast Greenland "a month earlier than what was normal in the past."

    "We expected to face some sea ice but everything was gone in the fjords upon our arrival," he added. "The sea water temperature in the fjords was also unbelievably high."

    Another expert on the cruise called the outside temperature "surprisingly warm." 

    "It was T-shirt weather," Paul Berkman, an environmental science professor at the University of California Santa Barbara, told NBC News. Berkman noted two other major Arctic developments over the summer:

    Berkman said the polar regions, and the Arctic in particular, show an "amplified response" to a warming climate ahead of other parts of the globe.

    That response is twofold, he adds: Arctic temperatures have warmed 3-6 degrees F above the global average, and reduced ice removes huge amounts of reflective white from the sea and reveals a dark sea that absorbs heat.

    The sea ice is like "a giant mirror on Earth's surface" he said. "Without summer Arctic sea ice, more heat from the sun is absorbed into the Earth system, which is a feedback that further accelerates warming of our climate."

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  • Polar bear cannibalism: More to come in a warmer Arctic?

    Jessica Robertson / USGS

    Sea ice is critical habiat for polar bears, which use it as platforms from which to hunt seals.

    By Miguel Llanos, NBC News

    Adult male polar bears preying on cubs and even females has long been observed, but recent sightings off Norway suggest that cannibalism may happen more often as warming temperatures reduce Arctic sea ice, a leading polar bear scientist says in a new report.

    The conclusion is based on images and observations made of three separate cannibalism incidents in summer and early fall while the adult polar bears were on sea ice, which polar bears use as platforms to hunt seals.

    Most previous cannibalism observations have involved polar bears on the shoreline and later in the year.

    "The three observations we describe are different from most other reports of infanticide and cannibalism in polar bears because they took place between midsummer and early autumn, while some bears of all age and sex classes were still actively using the remaining sea ice as a platform from which to hunt," wrote Ian Stirling, a polar bear expert with Canada's environmental agency, and Jenny E. Ross, a photographer who captured images of an incident on July 21, 2010.

    Dec. 10, 2009: Tourists visiting Churchill, Canada, were shocked to see an adult polar bear eating a cub. CBC's Mychaylo Prystupa reports wildlife experts say bear cannibalism is becoming more common due to changes in the food supply.

    Because few earlier observations of polar bears on summer sea ice have been made, such cannibalism "may be relatively normal and possibly occurs more frequently than has previously been thought," the authors wrote in the study published in the December issue of the peer-reviewed journal Arctic.

    "However, as the climate continues to warm and sea ice continues to break up and melt at earlier dates, thus making seals less available earlier in the summer, the frequency of intraspecific predation and cannibalism may increase," they added. "Similarly, as more ships go farther into the disintegrating ice to view and photograph polar bears, it is likely that similar instances of intraspecific predation and cannibalism on the sea ice will be reported more frequently."

    Arctic 'not cooling as well as it used to'

    Arctic sea ice follows a natural cycle of growing in winter and shrinking in summer, but in the last decade the shrinkage has spread.

    Last September, "sea ice covering the Arctic Ocean fell to the second-lowest extent in the satellite record, which began in 1979," the National Snow and Ice Data Center reported last October.

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